This the best advice here, just throw in bearings, a pinion that doesn't wear out in 3 runs, and whatever cheap no-name servo that you can get your hands on.I wouldn't put any money into a TT02. Not a single penny. Just build it and drive it.
I've owned several highly hopped-up TT02s, including a Type S. The best "upgrade" for a TT02 is to save up buy a better chassis.